The present disclosure relates to light scanning devices that write and form images by scanning light beams and that are used in image forming apparatuses such as printers, copiers, and facsimile machines.
Conventional image forming apparatuses using the electrophotographic method are equipped with light scanning devices that scans light beams (laser light) modulated according to input image data across the surface of a photosensitive drum charged uniformly by a charger. In such image forming apparatuses, an image forming process is performed in the following steps: an electrostatic latent image is formed by a light scanning device, the electrostatic latent image is developed into a toner image by a developing device, the toner image is transferred onto a recording sheet of paper or the like, and then the transferred toner image is fixed into a permanent image by a fixing device.
Such a light scanning device includes a light source such as a laser diode (LD), and optical components such as a polygon mirror, a scanning lens, and a plane mirror, which are accommodated inside a housing. Among the units constituting an image forming apparatus, a light scanning device is a high precision device, and thus factors such as vibration and thermal deformation due to high-speed rotation of the polygon mirror need to be taken into consideration in designing the configuration of the light scanning device.
For example, there is known a light scanning device fitting structure such that units constituting a light scanning device are first mounted on an inside of a top panel of a housing case having an open bottom face, then the housing case is fixed to tie bars placed on a pair of right and left jig blocks, and then the housing case is fitted and fixed to a main frame of a printer, together with the tie bars.
There is also known a light scanning device including a first frame that holds a plurality of optical components including a light beam generator and a light deflector, a second frame that holds light-beam direction changing means that receives a light beam output from the last-stage optical component of the first frame and emits light in a direction toward an image forming surface, frame uniting means that unites the first and second frames by fixing them to each other with the second frame positioned with respect to the first frame, and frame fixing means that fixes the united first and second frames independently to different predetermined stationary members.
There is also known a light scanning device in which positioning and fixing in a height direction is achieved by three of a plurality of positioning portions provided in an optical box, and apart from the three positioning portions, an elastic member is provided via which to achieve pressing down in the height direction. There is also known a light scanning device that has at least one positioning plate for positioning an optical box with respect to supporting means for supporting the optical box, the positioning plate including first and second positioning portions disposed oriented in different directions from each other, positioning of the optical box being performed by means of the first or second positioning portion.